It is well known for a hospital stretcher to have a hydraulic arrangement which can raise and lower the mattress on which a patient is supported. Typically, the hydraulic arrangement includes two fluid actuated cylinders provided at spaced locations on the base of the stretcher and each having an upwardly extending piston rod which is pivotally coupled at its upper end to a support frame for the mattress of the stretcher. Traditionally, the hydraulic arrangement is mechanically operated, for example by foot pedals. For example, a first foot pedal may be repeatedly pressed to pump fluid into both of the cylinders in order to raise the mattress, a second foot pedal can be pressed to bleed fluid from one of the cylinders, and a third foot pedal can be pressed to bleed fluid from the other of the cylinders. These known mechanical arrangements can be tiring to operate. Further, hospital personnel sometimes try to operate two or more of the pedals at once for efficiency, for example the pedal which operates the pump and one of the pedals controlling a bleed valve. This is not only awkward, but presents a degree of danger in view of the fact that the person is trying to use each foot to operate a respective pedal and thus may lose his or her balance.
Because of these disadvantages of known mechanical arrangements, interest has developed in electrical controls. One existing stretcher has a scissors mechanism rather than a hydraulic arrangement to permit vertical adjustment of the mattress and patient, and the scissors mechanism is electrically operated by a microprocessor-based circuit controlled by manually operable switches. However, a disadvantage of this system is that the circuitry requires electricity to operate, and there is not always a handy wall outlet into which the power cord for the stretcher can be plugged.
An object of the present invention is therefore to provide a stretcher having a hydraulic arrangement for adjusting the vertical position of a patient and having both electrically powered and mechanically powered systems for controlling the hydraulic arrangement.
A further object of the invention is to provide such a stretcher in which, when an adjustment in the inclination of the patient support surface is needed, appropriate control of both fluid actuated cylinders will be automatically effected.